Myxedema coma with an unfortunate clinical course: An autopsy case report

Myxedema coma (MC) is an uncommon but serious endocrine emergency stemming from untreated hypothyroidism and other triggers, leading to multiorgan dysfunction with a mortality rate of approximately 30%. This report details an 83-year-old male patient with chronic heart failure who initially presented with impaired consciousness. He had recently been diagnosed with hypothyroidism (TSH 57 mIU/L, FT4 0.56 ng/dL) prior to hospitalization and had started Levothyroxine (LT4) therapy. Upon admission, the patient presented with drowsiness (Glasgow Coma Scale score of 3), a low respiratory rate, hyponatremia (125 mEq/L), and respiratory acidosis (pCO2 85 torr). Despite prior LT4 therapy, severe hypothyroidism persisted (TSH 118.0 mIU/L, FT4 0.38 ng/dL). MC was diagnosed based on impaired consciousness, hypothyroidism, hyponatremia, and hypercapnia. Treatment included 200 μg of LT4 administered via a nasogastric tube and an initial intravenous dose of 100 mg hydrocortisone. The patient’s consciousness and TSH level improved (TSH 3.35 mIU/L by day 20), and hyponatremia was corrected. However, hypercapnia worsened, necessitating non-invasive positive pressure ventilation (NIPPV) on day 10, which initially resulted in clinical improvement. Subsequently, NIPPV-associated aspiration pneumonia developed. Despite antibiotic treatment and transient improvement, the patient’s respiratory condition deteriorated after a failed NIPPV weaning attempt. The patient died from respiratory failure on day 30. Autopsy revealed atrophic thyroid follicles with signs of interfollicular fibrosis and minimal lymphocyte infiltration. Advanced age and the need for mechanical ventilation were suggested as critical risk factors for mortality in MC caused by refractory hypercapnia and aspiration pneumonia.